Abstract

Background

West Nile virus infection in humans in urban areas of the Midwestern United States
has exhibited strong spatial clustering during epidemic years. We derived urban landscape
classes from the physical and socio-economic factors hypothesized to be associated
with West Nile Virus (WNV) transmission and compared those to human cases of illness
in 2002 in Chicago and Detroit. The objectives were to improve understanding of human
exposure to virus-infected mosquitoes in the urban context, and to assess the degree
to which environmental factors found to be important in Chicago were also found in
Detroit.

Results

Five urban classes that partitioned the urban space were developed for each city region.
The classes had many similarities in the two settings. In both regions, the WNV case
rate was considerably higher in the urban class associated with the Inner Suburbs,
where 1940–1960 era housing dominates, vegetation cover is moderate, and population
density is moderate. The land cover mapping approach played an important role in the
successful and consistent classification of the urban areas.

Conclusion

The analysis demonstrates how urban form and past land use decisions can influence
transmission of a vector-borne virus. In addition, the results are helpful to develop
hypotheses regarding urban landscape features and WNV transmission, they provide a
structured method to stratify the urban areas to locate representative field study
sites specifically for WNV, and this analysis contributes to the question of how the
urban environment affects human health.